It is known that power plants and other industries utilize ion exchange resins to purify water used in producing steam. The rate at which ion exchange occurs at exchange sites on resin is referred to as ion exchange kinetics, and is expressed as the mass transfer coefficient (MTC), or the speed at which an exchange site on a resin bead removes ionic impurities from service water through polar attraction. Excellent resin kinetics implies the resin is able to attract and remove impurities before the water carries them past ion exchange sites, and can be summarized as, “The better the kinetic properties are on resin, the higher the quality of effluent waters it will produce.” Organic materials and iron oxides adhering to the surface of resins can block exchange sites, slowing the ability of the resin to attract and remove impurities. Blocking exchange sites on resin surfaces results in higher levels of impurities remaining in effluent waters.
To control corrosion rates in plant equipment, the power industry elevates the pH of process waters with various organic amines. Organic additives chemically break down in regions of high temperatures. The resulting decomposition products are captured on surfaces of ion exchange resins, causing the resins to become fouled.
It has recently been determined that decomposition products of pH control additives such as Monoethanolamine (ETA/MEA) are captured on resins as both, positively and negatively charged anions, resulting in ETA/MEA organic complexes. Current resin regeneration processes are unable to effectively remove anionic ETA, or organic and iron oxide foulants from resin surfaces, rendering anion resins incapable of performing ion exchange. Degraded kinetic properties due to organic fouling, results in increased chloride, sulfate and silica slippage from ion exchangers during service runs. Impurities in industrial feedwaters challenge chemistry goals designed to minimize corrosion. Typically, kinetically fouled resin must be removed from service, discarded, and replaced with new. The system and method of this invention removes undesirable foulants from the surface of resins, enabling extended life spans for resin.
Replacing resin charges is extremely costly, and if discarded resin is contaminated with detectible isotopic activity (nuclear power) the cost to bury as radwaste significantly increases replacement costs. Previously, no known acceptably safe or effective method has existed for removing organic fouling and iron oxides from the surface of resin beads. The system and method of this invention efficiently cleans and restores resin ion exchange kinetics by removing all organic materials, resin surface-loaded iron oxides, resin fines, suspended iron oxides, with regenerations that provide final rinse qualities exceeding the levels of new resins.
The increasing demands in the utility sector to lower feedwater impurities as a result of resin maintenance activities are well documented gaps in maintaining health and readiness of condensate polishing resins. Conventional regeneration methods are unable to maintain ion exchange kinetics on polisher resins. Uncommon innovations have been integrated into the system and method of this invention to effectively remove resin fines, suspended and attached iron, and organic/organometallic materials from resins. Additionally, this invention facilitates removal of radioactive material from waste nuclear resins, to levels allowing release as landfill grade waste.
Few solutions to this issue can be found in prior art. For example, sodium bisulfite has been proposed as a solution for removing rust from water softeners, as taught by Hatch (U.S. Pat. No. 3,139,401), however the solution lacks the efficacy and simplicity of the system and method of the present invention. Other resin regeneration chemicals have been previously patented for their anion/cation resin separation properties, but the scope of the application as taught by Auerswald (U.S. Pat. No. 4,511,675) is limited.